Cooling/Check Engine somewhat of a problem

First off, something has been going wrong with my xj every week for the past month and i have been able to fix it, but this one blows my mind. people keep telling me to sell it for something reliable and i just laugh. sorry if this is long but i want to spill the details so you know exactly what i did. It started with an oil change when i realized my valve cover and oil pan gaskets were barely leaking so i replaced the oil pan with a rubber gasket and the valve cover with rtv gasket stuff. well i apparently cut one of the smaller coolant hoses when dealing with the valve cover so i lost a lot of coolant. so i replaced the hose and cleaned out the coolant reservoir, after i patched up a crack i found in the bottom that previously was covered with crap. after all this i started the jeep up and it was puttering at first, the check engine light came on, and the cooling fan was on (after being room temperature for a long time). so i ran it a bunch of times getting air bubbles out of the coolant lines and making sure the coolant in the radiator cap is full, but nothing changes. so i took it to a friend of mine who has a computer reader and it said there was a problem with the coolant temperature being too high. it also said the coolant temperature was at 104 and we tried shorting the wires and it wouldnt change from 104. but yet my cooling fan is always on. i just drive it anyways cause the dash engine temp gauge is at normal summer temps never getting close to the red. i was thinking maybe it had to do with the coolant temp sensor but why does the computer say its too hot and it reads 104 at the same time????

oh yeah, its a 93 xj sport automatic w/ 4.5 lift and 32s 4.10s and a new straight 6 (same 93 design) with about 10,000 miles (cause of a thrown rod through the block)

the temp sensor in the thermostat housing is either disconnected or bad. It will make the check engine light stay on and make the fan run all the time.

As for the temp of 104, where did that reading come from?

it came from the computer that we hooked up to the jeep to read the codes for the check engine light.

Jess said:

the temp sensor in the thermostat housing is either disconnected or bad. It will make the check engine light stay on and make the fan run all the time.

Click to expand...

Exactly.

well i know its not disconnected, but shouldnt unpluging it or shorting the wires change the temperature reading? i guess ill just replace the sensor and hope that fixes everything...